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Diffstat (limited to 'fs/fdos/fat.c')
| -rw-r--r-- | fs/fdos/fat.c | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/fs/fdos/fat.c b/fs/fdos/fat.c new file mode 100644 index 0000000..42df755 --- /dev/null +++ b/fs/fdos/fat.c @@ -0,0 +1,145 @@ +/* + * (C) Copyright 2002 + * Stäubli Faverges - <www.staubli.com> + * Pierre AUBERT p.aubert@staubli.com + * + * See file CREDITS for list of people who contributed to this + * project. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of + * the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, + * MA 02111-1307 USA + */ + +#include <common.h> +#include <config.h> +#include <malloc.h> + +#if (CONFIG_COMMANDS & CFG_CMD_FDOS) + +#include "dos.h" +#include "fdos.h" + + +/*----------------------------------------------------------------------------- + * fat_decode -- + *----------------------------------------------------------------------------- + */ +unsigned int fat_decode (Fs_t *fs, unsigned int num) +{ + unsigned int start = num * 3 / 2; + unsigned char *address = fs -> fat_buf + start; + + if (num < 2 || start + 1 > (fs -> fat_len * SZ_STD_SECTOR)) + return 1; + + if (num & 1) + return ((address [1] & 0xff) << 4) | ((address [0] & 0xf0 ) >> 4); + else + return ((address [1] & 0xf) << 8) | (address [0] & 0xff ); +} +/*----------------------------------------------------------------------------- + * check_fat -- + *----------------------------------------------------------------------------- + */ +static int check_fat (Fs_t *fs) +{ + int i, f; + + /* Cluster verification */ + for (i = 3 ; i < fs -> num_clus; i++){ + f = fat_decode (fs, i); + if (f < FAT12_LAST && f > fs -> num_clus){ + /* Wrong cluster number detected */ + return (-1); + } + } + return (0); +} +/*----------------------------------------------------------------------------- + * read_one_fat -- + *----------------------------------------------------------------------------- + */ +static int read_one_fat (BootSector_t *boot, Fs_t *fs, int nfat) +{ + if (dev_read (fs -> fat_buf, + (fs -> fat_start + nfat * fs -> fat_len), + fs -> fat_len) < 0) { + return (-1); + } + + if (fs -> fat_buf [0] || fs -> fat_buf [1] || fs -> fat_buf [2]) { + if ((fs -> fat_buf [0] != boot -> descr && + (fs -> fat_buf [0] != 0xf9 || boot -> descr != MEDIA_STD)) || + fs -> fat_buf [0] < MEDIA_STD){ + /* Unknown Media */ + return (-1); + } + if (fs -> fat_buf [1] != 0xff || fs -> fat_buf [2] != 0xff){ + /* FAT doesn't start with good values */ + return (-1); + } + } + + if (fs -> num_clus >= FAT12_MAX_NB) { + /* Too much clusters */ + return (-1); + } + + return check_fat (fs); +} +/*----------------------------------------------------------------------------- + * read_fat -- + *----------------------------------------------------------------------------- + */ +int read_fat (BootSector_t *boot, Fs_t *fs) +{ + unsigned int buflen; + int i; + + /* Allocate Fat Buffer */ + buflen = fs -> fat_len * SZ_STD_SECTOR; + if (fs -> fat_buf) { + free (fs -> fat_buf); + } + + if ((fs -> fat_buf = malloc (buflen)) == NULL) { + return (-1); + } + + /* Try to read each Fat */ + for (i = 0; i< fs -> nb_fat; i++){ + if (read_one_fat (boot, fs, i) == 0) { + /* Fat is OK */ + fs -> num_fat = i; + break; + } + } + + if (i == fs -> nb_fat){ + return (-1); + } + + if (fs -> fat_len > (((fs -> num_clus + 2) * + (FAT_BITS / 4) -1 ) / 2 / + SZ_STD_SECTOR + 1)) { + return (-1); + } + return (0); +} + + + + +#endif |